There are a number of major types of illuminated sign technologies presently in use. A first type are surface-painted signs which are illuminated by external light sources, such as floodlights, which are generally located at acute angles to the sign. Light energy is wasted since, a) the entire sign surface is illuminated (not just the message), and b) a great percentage of the light reflected never reaches the observer either being spilled off to the sky or ground.
A second type of illuminated sign is a lighted box sign where a light source is placed behind a translucent surface (that can provide structural support for the sign) with the message spelled out on the translucent surface, in characters contrasting to the translucent surface background. Light energy is produced to provide equal luminous emission over the face of the sign, including the background, as opposed to lighting only the character which has to be seen. Only a small fraction of the light produced reaches the eye of the observer, as the light exits the sign in all directions including upwards, thus wasting energy and causing a considerable amount of light pollution.
A third type of illuminated sign includes signs including light sources which themselves spell out the sign message. Neon signs, exposed incandescent filament lamp signs and channel letters are examples of this technology. When not lit, these signs are not readily visible (unless paint is applied under the character or symbol) and are thus totally dependent on being illuminated to deliver the message. These signs are costly to make, operate and maintain as they are custom made for the client, of limited life span, fragile and the incandescent version is energy wasteful.
A fourth type of illuminated sign includes an LED matrix sign. LED technology is taken advantage of to create changing-message signs. These dynamic message signs are computer-controlled and provide interesting and attention-grabbing signs which are a solution to illuminated signs with the need for a changing message.
However, most illuminated signs are of a fixed message, and these signs are initially expensive and costly to operate and maintain.